KR20230047961A - High precision nanoscale thin film manufacturing process - Google Patents

Abstract

A method of fabricating one or more elements in a multilens column is provided. Ultraviolet (UV) curable droplets are dispensed with an inkjet on a substrate that can be supported by a chuck. The spreading and coalescing of the inkjet droplets then forms a non-uniform liquid film. The film is then locally heated using a digital micromirror element array or the like. The film is then cured by exposure to UV light, where the cured film together with the substrate forms elements of a multi-lens column. The substrate is then moved to a metrology station where optical metrology is performed on the cured film and substrate for quality control.

Description

High precision nanoscale thin film manufacturing process

(Cross Reference to Related Applications)

This application claims priority to U.S. Provisional Patent Application Serial No. 63,026,215, entitled "High Precision Nanoscale Thin Film Fabrication Processes," filed on May 18, 2020, which The content of is incorporated herein by reference. This application also claims priority to U.S. Provisional Patent Application Serial No. 63/031,681, filed on May 29, 2020, entitled "High Precision Nanoscale Thin Film Fabrication Processes", , the contents of this application are incorporated herein by reference.

The present invention relates generally to nanoscale thin film deposition, and more particularly to the production of optical elements in multi-lens columns using a nanoscale precision programmable profiling (nP3) process. It's about manufacturing.

Current state-of-the-art semiconductor patterning includes feature sizes smaller than 100 nm and in some cases as small as 10 nm. For such high-resolution features, wavelengths of visible light are not sufficient because the resolution is directly proportional to the wavelength. Therefore, electromagnetic radiation in the deep UV spectrum is required. Commonly used wavelengths include 248 nm (Hg vapor), 193 nm (excimer laser) and 157 nm (vacuum UV). At the same time, the resolution increases as the numerical aperture of the system, which is generally greater than 0.9, increases. Such high resolution can theoretically be achieved using large diameter lenses. However, these lenses are typically difficult to manufacture and align, difficult to mount into a system, and expensive. In order to overcome these constraints, these optical systems are designed with a large number of lens elements, typically greater than 10. By using multiple elements, it is possible to achieve high numerical apertures by using small elements for each aperture that individually have low numerical apertures but can function together to obtain a desired value.

However, the use of multiple elements in an optical system presents other difficulties. One of these difficulties is that there are “gaps” between the individual elements. Ideally, it is desirable to use optical cements in these gaps to minimize the refractive index mismatch at the optical element-gap interface. However, the use of excimer lasers and other UV radiations can rapidly degrade the quality of the bonding agent, precluding the use of such bonding agents. So instead of using a bonding agent, the gap can be left as is. That is, the gaps may become air gaps. Because of this, a large refractive index mismatch occurs between the optical element and the air gap, so it is important to design an optical system such that the angle of incidence and angle of refraction do not exceed the critical angle for total internal reflection. Also, the entire optical system must be designed in such a way that the total optical aberrations of the system do not exceed a value capable of distorting the image.

In one embodiment of the present invention, a method of fabricating one or more elements in a multi-lens column includes inkjet dispensing ultraviolet (UV) curable droplets onto a substrate. The method further includes forming a non-uniform liquid film by spreading and merging the inkjet droplets. The method further includes locally heating the membrane. The method also includes curing the film by exposing it to UV light, where the cured film together with the substrate forms an element of a multi-lens column. Additionally, the method involves performing optical metrology on the cured film and substrate.

In another embodiment of the present invention, a method of fabricating one or more elements in a multi-lens column may include a lens imprecision to correct for extrinsic or intrinsic aberrations using a nanoscale precise programmable profiling process. It includes the process of depositing a hardened film on the surface of. The nanoscale precise programmable profiling process involves dispensing ultraviolet (UV) curable droplets onto a substrate with an inkjet. The nanoscale precise programmable profiling process further includes forming a non-uniform liquid film by spreading and merging inkjet droplets. The nanoscale precise programmable profiling process further includes locally heating the film using a digital micromirror device array. In addition, the nanoscale precise programmable profiling process involves curing the film by exposing it to UV light. The method further includes transferring the profile of the cured film to a substrate by dry etching, wherein the substrate with the transferred profile of the cured film forms an element of a multilens column.

In another embodiment of the present invention, a multilens column includes one or more optical elements fabricated using a nanoscale precision programmable profiling process and a dry etching process. The nanoscale precise programmable profiling process involves dispensing ultraviolet (UV) curable droplets onto a substrate with an inkjet. The nanoscale precise programmable profiling process further includes forming a non-uniform liquid film by spreading and merging inkjet droplets. The nanoscale precision programmable profiling process further includes locally heating the film. In addition, the nanoscale precise programmable profiling process involves curing the film by exposing it to UV light. Additionally, the nanoscale precise programmable profiling process includes transferring the profile of the cured film to a substrate by a dry etching process, where the substrate with the transferred profile of the cured film forms the optical element of the multilens column.

The foregoing has outlined rather generally the features and technical advantages of one or more embodiments of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the present invention will be described hereinafter which may form the subject of the claims of the present invention.

The present invention may be better understood when the following detailed description is considered in conjunction with the following drawings.
1 is a flow diagram of a method for a Nanoscale Precision Programmable Profiling (nP3) process on a nominally non-flat substrate according to one embodiment of the present invention.
2 is a method of manufacturing an element for a multi-lens column or the like on a non-flat substrate using a nanoscale precision programmable profiling (nP3) process without using a superstrate according to an embodiment of the present invention. It is a flow chart.
3A to 3E are cross-sectional views for manufacturing an element for a multi-lens column or the like using the nP3 process on a non-planar substrate without using an upper plate using the processes described in FIG. 2 according to an embodiment of the present invention. shows
4 is a flowchart of a method for manufacturing elements for a multi-lens column or the like on a flat substrate using a nanoscale precision programmable profiling (nP3) process without using a top plate according to an embodiment of the present invention.
5A to 5E are cross-sectional views for manufacturing an element for a multi-lens column or the like on a flat substrate using an nP3 process without using an upper plate using the processes described in FIG. 4 according to an embodiment of the present invention. show
6 is a flowchart of a method for fabricating an element for a multi-lens column or the like on a flat substrate using a nanoscale precision programmable profiling (nP3) process using a top plate according to an embodiment of the present invention.
7A to 7E are cross-sectional views for manufacturing an element for a multi-lens column or the like on a flat substrate using an nP3 process using an upper plate using the processes described in FIG. 6 according to an embodiment of the present invention. do.
8 is a flowchart of a method for manufacturing an element for a multi-lens column using an nP3 process for an imprecise lens according to an embodiment of the present invention.
9A-9C show cross-sectional views for fabricating an element for a multi-lens column or the like using the nP3 process for inaccurate lenses using the procedures described in FIG. 8 in accordance with one embodiment of the present invention.
10 is a flow diagram of an alternative method for fabricating elements for a multilens column using the nP3 process for imprecise lenses in accordance with one embodiment of the present invention.
11A-11C show cross-sectional views for fabricating elements for multiple lens columns and the like using the nP3 process for inaccurate lenses using the procedures described in FIG. 10 according to one embodiment of the present invention.
12 shows an example of a multi-lens optical system according to an embodiment of the present invention.
13 shows an element fabricated using nP3 that is part of an original system according to one embodiment of the present invention.
14 shows corrector plates fabricated using the nP3 process and added to the original system to improve optical performance and to mitigate design, manufacturing, and assembly tolerances for other elements of the system, according to one embodiment. .

As noted in the background, current state-of-the-art semiconductor patterning includes feature sizes smaller than 100 nm and in some cases as small as 10 nm. For such high-resolution features, wavelengths of visible light are not sufficient because the resolution is directly proportional to the wavelength. Therefore, electromagnetic radiation in the deep UV spectrum is required. Commonly used wavelengths include 248 nm (Hg vapor), 193 nm (excimer laser) and 157 nm (vacuum UV). At the same time, the resolution increases as the numerical aperture of the system, which is generally greater than 0.9, increases. Such high resolution can theoretically be achieved using large diameter lenses. However, these lenses are typically difficult to manufacture and align, difficult to mount into a system, and expensive. In order to overcome these constraints, these optical systems are designed with a large number of lens elements, typically greater than 10. By using multiple elements, it is possible to achieve high numerical apertures by using small elements for each aperture that individually have low numerical apertures but can function together to obtain a desired value.

However, the use of multiple elements in an optical system presents other difficulties. One of these difficulties is that there are “gaps” between the individual elements. Ideally, it is desirable to use optical cements in these gaps to minimize the refractive index mismatch at the optical element-gap interface. However, the use of excimer lasers and other UV radiations can rapidly degrade the quality of the bonding agent, precluding the use of such bonding agents. So instead of using a bonding agent, the gap can be left as is. That is, the gaps may become air gaps. Because of this, a large refractive index mismatch occurs between the optical element and the air gap, so it is important to design an optical system such that the angle of incidence and angle of refraction do not exceed the critical angle for total internal reflection. Also, the entire optical system must be designed in such a way that the total optical aberrations of the system do not exceed a value capable of distorting the image.

The principles of the present invention are applied to develop an optical system having a total optical aberration of the system that does not exceed a value that would distort the image beyond a desired tolerance for semiconductor wafer inspection.

Referring in detail to the drawings, FIG. 1 is a flow diagram of a method 100 for a nanoscale precision programmable profiling (nP3) process on a nominally non-flat substrate. Although the following description is for a substrate with a nominal curvature, other substrate profiles such as planar, aspheric, freeform, etc. can be processed in the same process.

Referring to Figure 1, in process 101, a profile or other characteristic of a substrate is measured.

In step 102, a pattern of droplets of profiling material is created and dispensed onto a substrate or superstrate. In one embodiment, the top is nominally a non-patterned roll of a flexible material such as polycarbonate, PET, PEN, etc., but may also be a textured or patterned roll, wherein the texture or pattern is The lateral space length scale is at least one order of magnitude smaller than the lateral space length scale of the desired profile.

In one embodiment, the supernatant web speed is synchronized with the dispense timing cycle to maintain droplet placement accuracy. In one embodiment, the droplet location corresponds to a desired location on the substrate such that the droplet is located where it should be on the substrate upon conformal contact with the substrate.

In step 103, the top region with the deposited droplets is traversed to a profiling zone under an ultraviolet (UV) lamp and a UV-transparent chuck. Tension in the top plate is adjusted to the desired level as required for the final surface profile. In one embodiment, a UVT chuck is used to hold the top in place.

In step 104, a vertical chuck motion (VCM) stage with the substrate mounted on the chuck is moved to the profiling area with the aid of a horizontal XY stage. The VCM stage can be actuated using voice coils, piezoelectric actuators, pneumatic actuators, and the like. In one embodiment, the chuck may be a 3-pin mount to support various curvatures. In one embodiment, vertical tip tilt motion of the VCM stage enables proper alignment and gap control of the superstrate and substrate.

At step 105, the air pressure is increased within the cavity to create curvature of the superstrate web so that the droplets merge to form adjacent films. This can relieve trapped air bubbles. A camera mounted on the UVT chuck is used to observe bubble entrapment. Air bubbles are identified by image processing and air is automatically injected into the top plate at the target location to spread the droplets and reduce the bubbles.

In process 106, the liquid film (adjacent film) is directed to an infrared radiation source projected through an array of digital micromirror elements or a distributed micro-heater or stage capable of rapidly scanning the entire substrate. It is locally heated with the aid of a spatially modulated thermal actuator, such as a laser source mounted on the Localized heating allows further control of the film thickness profile.

In process 107, the profiling material is UV cured after a certain amount of time required for capillary and thermal forces to create the desired topography. The VCM stage is used to separate the substrate from the top plate through vertical motion.

At step 108, the substrate is moved along with the VCM stage to a metrology station. The VCM stage helps align the normal to the curvature of the substrate at the point of measurement using the optical axis of a measurement system such as an interferometer, aberrometer or a Shack-Hartmann wavefront sensor. The laser beam is transmitted through an automatic telescopic system through the substrate and into the measurement system (to account for the different powers). An XY stage is used to scan a substrate in a horizontal plane to measure features at any position on the substrate. Once the measurements are taken, it is determined whether further processing is required (in the case of multi-process processes or to compensate for errors in previous processes). When processing is required, a horizontal stage brings the substrate back to the profiling area. In one embodiment, the communication module of the equipment may be used to transmit and exchange data related to substrate metrology, equipment sensors, and droplet patterns.

2 is a method 200 for manufacturing an element for a multi-lens column or the like on a non-planar substrate using a nanoscale precision programmable profiling (nP3) process without using a top plate according to an embodiment of the present invention. is the flow chart of 3A to 3E are cross-sectional views for manufacturing an element for a multi-lens column or the like using the nP3 process on a non-planar substrate without using an upper plate using the processes described in FIG. 2 according to an embodiment of the present invention. shows

Referring to FIG. 2 along with FIGS. 3A-3E , in process 201 , a droplet of UV curable liquid 301 (eg, mrUVCur26-SF from MicroResist® Technologies) is deposited on a non-planar substrate 303 as shown in FIG. 3A . ) is dispensed with the inkjet 302 on. In one embodiment, the amount of UV curable liquid 301 dispensed into the inkjet 302 is based on the desired film thickness profile.

In step 202, the desired non-uniform liquid film 304 is formed by spreading and merging the inkjet droplets 301 as shown in FIG. 3B.

In process 203, film 304 is locally heated using a digital micromirror device (DMD) array 305 as shown in FIG. 3C. In one embodiment, the DMD array 305 (eg, a digital light processing (DLP) chipset from Texas Instruments®) is an array of highly reflective aluminum micromirrors that reflect infrared (IR) light to, such as film 304. Corresponds to an optical microelectromechanical system (micro-electrical-mechanical system; MEMS) including. In one embodiment, infrared (IR) light consists of a wavelength range between 1,000-11,000 nm. In one embodiment, the IR light source is an IR laser. In one embodiment, localized heating of film 304 is performed using one or more of the following: a projected infrared light source using DMD array 305, a distributed microheater, and a stage-mounted infrared light source. laser source.

In one embodiment, use of the DMD array 305 enables ultra-precise profiling with spatio-temporal control of thermal and flow gradients.

In step 204, after a certain amount of time required for capillary and thermal forces to create the desired shape, the film 304 is UV cured by exposing it to UV light 306 to form a cured film 307. formed, which together with the substrate 303 form an element of a multi-lens column as shown in FIG. 3d.

At step 205, the substrate 303 is brought to a metrology station where optical metrology 308 is performed on the substrate 303 and the cured film 307 for quality control as shown in FIG. 3E. are moved In one embodiment, optical metrology is performed in situ simultaneously with steps 202 and 203 to enable real-time feedback and control.

In one embodiment, a selective reaction ion or dry etching process may be performed following the nP3 process.

4 is a method 400 for manufacturing an element for a multi-lens column or the like on a flat substrate using a nanoscale precision programmable profiling (nP3) process without using a top plate according to an embodiment of the present invention. It is a flow chart. 5A to 5E are cross-sectional views for manufacturing an element for a multi-lens column or the like on a flat substrate using an nP3 process without using an upper plate using the process described in FIG. 4 according to an embodiment of the present invention. show

Referring to FIG. 4 along with FIGS. 5A-5E , in step 401 , a UV curable droplet 501 is sprayed by an inkjet 502 onto a flat substrate 503 supported by a chuck 504 as shown in FIG. 5A . ) is distributed. In one embodiment, the amount of UV curable liquid 501 dispensed into the inkjet 502 is based on the desired film thickness profile.

In step 402, the spreading and merging of inkjet droplets 501 forms a desired non-uniform liquid film 505, as shown in FIG. 5B.

In process 403, film 505 is locally heated using a digital micromirror device (DMD) array 506 as shown in FIG. 5C. In one embodiment, the DMD array 506 (eg, a digital light processing (DLP) chipset from Texas Instruments®) includes an array of highly reflective aluminum micromirrors that reflect IR light onto, such as film 505 . It corresponds to the micro-electrical-mechanical system (MEMS). In one embodiment, the IR light consists of a wavelength range between 1,000-11,000 nm. In one embodiment, the IR light source is an IR laser. In one embodiment, localized heating of membrane 505 is performed using one or more of the following: a projected infrared light source using DMD array 506, a distributed microheater, and a stage-mounted infrared light source. laser source.

In one embodiment, use of the DMD array 506 enables ultra-precise profiling with spatiotemporal control of thermal and flow gradients.

At step 404, after a certain amount of time required for capillary and thermal forces to create the desired shape, the film 505 is UV cured by exposing it to UV light 507 to form a cured film 508. formed, which together with the substrate 503 form an element of a multi-lens column as shown in FIG. 5d.

In process 405, the substrate 503 is moved to a metrology station for quality control as shown in FIG. 5E. Optical metrology 509 is performed on the cured film 508 and substrate 503 at the metrology station. In one embodiment, optical metrology is performed in situ simultaneously with steps 402 and 403 to enable real-time feedback and control.

In one embodiment, a selective reactive ion or dry etch process may follow the nP3 process.

6 is a flowchart of a method 600 for manufacturing elements for a multi-lens column or the like on a flat substrate using a nanoscale precision programmable profiling (nP3) process using a top plate according to an embodiment of the present invention. am. 7A to 7E are cross-sectional views for manufacturing an element for a multi-lens column or the like on a flat substrate using an nP3 process using an upper plate using the processes described in FIG. 6 according to an embodiment of the present invention. do.

Referring to FIG. 6 along with FIGS. 7A-7E , in step 601 , a UV curable droplet 701 is sprayed by an inkjet 702 onto a flat substrate 703 supported by a chuck 704 as shown in FIG. 7A . ) is distributed. In one embodiment, the amount of UV curable liquid 701 dispensed into the inkjet 702 is based on the desired film thickness profile.

In step 602, the desired non-uniform liquid film 705 is formed by contacting the jetted UV curable droplets 701 with the superstrate 706 to spread and merge the inkjet droplets 701 as shown in FIG. 7B. do. In one embodiment, top 706 is nominally an unpatterned roll of a flexible material such as polycarbonate, PET, PEN, etc., but may also be a textured or patterned roll, where the lateral space length scale of the texture or pattern is at least one order of magnitude smaller than the lateral spatial length scale of the desired profile.

In process 603, film 705 is locally heated using a digital micromirror element (DMD) array 707 as shown in FIG. 7C. In one embodiment, the DMD array 707 (eg, a digital light processing (DLP) chipset from Texas Instruments®) includes an array of highly reflective aluminum micromirrors that reflect IR light to, such as film 705. Corresponds to optical microelectromechanical systems (MEMS). In one embodiment, the IR light consists of a wavelength range between 1,000-11,000 nm. In one embodiment, the IR light source is an IR laser. In one embodiment, localized heating of membrane 705 is performed using one or more of the following: a projected infrared light source using DMD array 707, a distributed microheater, and stage-mounted infrared light. laser source.

In one embodiment, use of the DMD array 707 enables ultra-precise profiling with spatiotemporal control of thermal and flow gradients.

In step 604, after a certain amount of time required for capillary and thermal forces to create the desired shape, the film 705 is UV cured by exposing it to UV light 708 to form a cured film 709. formed, which together with the substrate 703 form an element of a multi-lens column as shown in FIG. 7d.

In step 605, the top plate 706 is removed by etching or the like as shown in FIG. 7E.

At step 606, the substrate 703 is moved to a metrology station where optical metrology 710 is performed on the substrate 703 and the cured film 709 for quality control, as shown in FIG. 7E. In one embodiment, optical metrology is performed in situ simultaneously with steps 602 and 603 to enable real-time feedback and control.

In one embodiment, a selective reactive ion or dry etch process may be performed following the nP3 process.

8 is a flow diagram of a method 800 for fabricating elements for a multi-lens column using the nP3 process for imprecise lenses according to one embodiment of the present invention. 9A-9C show cross-sectional views for fabricating an element for a multi-lens column or the like using the nP3 process for inaccurate lenses using the procedures described in FIG. 8 according to one embodiment of the present invention.

Referring to FIG. 8 in conjunction with FIGS. 9A-9C , different types of glass (e.g., A thin film 902 is deposited using the nP3 process on the surface of an imprecise substrate 901 made of fused silica, quartz, BK-7, UV grade fused silica, etc.) or silicon. This process is intended to fabricate an ideal substrate.

In step 802, after curing, the thin film profile 903 is transferred by dry etching to the underlying substrate 901 to form the finished ideal lens as shown in FIG. 9C. In one embodiment, a substrate 901 with a transferred profile 903 forms an element of a multilens column.

10 shows a flow diagram of an alternative method 1000 for fabricating elements for a multilens column using the nP3 process for imprecise lenses in accordance with one embodiment of the present invention. 11A-11C show cross-sectional views for fabricating elements for multiple lens columns and the like using the nP3 process for inaccurate lenses using the procedures described in FIG. 10 according to one embodiment of the present invention.

Referring to FIG. 10 in conjunction with FIGS. 11A-11C , different types of glass (e.g., A thin film 1102 is deposited using the nP3 process on the surface of an imprecise substrate 1101 made of fused silica, quartz, BK-7, UV grade fused silica, etc.) or silicon. The goal of this process is to produce lenses with aberration corrections.

In process 1002, after curing, the thin film profile 1103 is transferred to the underlying substrate 1101 by dry etching to form a finished lens with aberration correction as shown in FIG. 11C. In one embodiment, the substrate 1101 with the transferred profile 1103 forms an element of a multilens column.

In one embodiment, the nP3 process is used in precision optics. Precision optical elements include mirrors and lenses for a variety of applications. Depending on the application, these elements may have to be fabricated from a variety of substrate materials, and may be flat, free-form or nominally curved. The nP3 process can be used to create a completely different profile from a starting substrate to modify the existing shape of the substrate to match a desired shape or to provide some functional property to the system, such as minimizing optical aberrations. In some applications, the nP3 process deposits a functional film that remains on the substrate. For example, for optical applications, the functional material may be a film with a refractive index matching that of the substrate. For some applications, the nP3 process deposits a sacrificial film that can be used to transfer the profile of the film to the substrate using an etch process. The relative etch rate ratio between the polymer film and the substrate or underlying film may vary from 0.02 to 50. Depending on this etch rate ratio, the sacrificial film profile can be modified to obtain the desired final profile on the substrate. The sacrificial film profile may be adjusted to compensate for systematic errors in a pre- or post-processing process such as an etching process. In some applications, the presence of a polymer film can degrade the substrate's functionality, such as high intensity laser beam optics, other advanced precision optics such as deep UV (DUV) microscope objectives, or semiconductors. Objectives used for wafer and mask metrology and characterization must be removed to enable functionality. In one embodiment, the etching process is performed in a reactive ion etching (RIE) chamber using a plasma process to obtain a desired ratio between the etch rate of the sacrificial profiling material and the underlying substrate material. The etching process itself can be divided into a plurality of coarse steps and fine steps, and a large amount of material can be removed in the coarse process at a high etching rate for high throughput. Correct the error in the desired profile. In one embodiment, intermediate metrology may be performed between the coarse and fine processes. Additionally, in some applications, a uniform film can be deposited in addition to the nP3 process film. For example, a uniform metal layer may be deposited after the nP3 process to provide the substrate with optically reflective properties with an appropriate profile.

In one embodiment, the nP3 process for precision optics may be exemplarily applied to semiconductor optical lithography, metrology, and inspection equipment.

Exemplary applications for optical elements fabricated using the nP3 process include semiconductor optical lithography, imaging, inspection, metrology, microscopy, characterization, and use during implementation of cameras and other systems requiring multiple lens columns. It includes a multi-lens optical system. In one embodiment, the nP3 process may be combined with RIE. Current state-of-the-art semiconductor patterning includes feature sizes well below 100 nm, in some cases down to 10 nm. For these high-resolution features, wavelengths of visible light are not sufficient because the resolution is directly proportional to the wavelength. Therefore, electromagnetic radiation in the deep UV spectrum is required. Commonly used wavelengths include 248 nm (Hg vapor), 193 nm (excimer laser) and 157 nm (vacuum UV). At the same time, the resolution increases as the numerical aperture of the system, which is generally greater than 0.9, increases. This could theoretically be achieved using a large-aperture lens. However, these lenses have traditionally been difficult and expensive to mount, as well as difficult to manufacture and align in a system. To accommodate these constraints, these optical systems are typically designed with a large number of lens elements, usually in excess of 10. By using multiple elements, it is possible to achieve high numerical apertures using small elements that individually have low numerical apertures but can function together to obtain a desired value for numerical aperture.

However, the use of multiple elements in an optical system presents other difficulties. One of these difficulties is that there are “gaps” between the individual elements. Ideally, an optical bonding agent should be used in this gap to minimize the refractive index mismatch at the optical element-gap interface. However, the use of excimer lasers and other UV radiations can rapidly degrade these binders, precluding their use. So instead of using a bonding agent, the gap can be left as is. That is, the gap may become an air gap. This causes a high refractive index mismatch between the optical element and the air gap, so it is important to design the optical system so that the angles of incidence and refraction do not exceed the critical angle for total internal reflection. Additionally, the entire optical system must be designed in such a way that the total optical aberrations of the system do not exceed values that would distort the image beyond desired tolerances. Typical specifications for optical aberrations include peak-to-valley (P-V) and/or root mean square (RMS) optical paths better than λ/30 for the entire system. Difference error and Strehl ratio (quality of forming an optical image of an optical element) of at least 0.9, often greater than 0.95. where λ is the wavelength of the light used. These specifications are usually directly transferred onto the individual elements themselves without much modification. These stringent performance specifications lead to tighter manufacturing tolerances and increase the cost of individual components. In addition, multi-lens optical systems have individual elements dedicated to the control of specific aberrations, such as polarization aberrations, on-axis aberrations (e.g. spherical aberrations) and off-axis aberrations (e.g. coma aberrations). can have Also, at short wavelengths, chromatic aberration can become significant despite the use of a substantially monochromatic light source and may need to be corrected using precision double and/or triple lenses. For example, fused silica exhibits a refractive index change of -0.007 over a bandwidth of +/- 5 nm at a wavelength of 248 nm. Similar refractive index changes are observed in most of the entire visible spectrum for BK-7 glass.

The nature of these aberrations is also determined after the individual elements have been mounted and aligned. Optical performance specifications therefore lead to tolerances for the mounting and alignment of individual elements, especially given that during shipping these elements and their mounts may be exposed to temperatures ranging from -40°C to 60°C. One or more elements in the column may be adjusted or translated to minimize the overall aberrations of the system during final qualification of the system. These aberrations can consist of polarization aberrations, chromatic aberrations and on-axis and off-axis aberrations.

The numerical aperture (NA) and optical aberrations can affect the achievable magnification of the system, which, combined with the size of the sensor array, leads to the definition of the field of view. This can be an important consideration as it is desirable to have a wide field of view to maximize system throughput. In general, as the NA increases, the working distance decreases, the resolution increases, the magnification increases, and the field of view decreases. If the aberration profile can be precisely controlled over a large area, a high NA (high magnification) can be achieved over a wider field of view. The inventive principles disclosed herein can increase the field of view without sacrificing the NA of the system. For example, the field of view of a multilens column is greater than 250 square millimeters and the multilens column is used in projection lithography. In the case of an imaging system, the field of view also depends on the size of the imaging sensor and can be given as a function of magnification according to the size of the sensor. For example, for an imaging sensor with a diagonal width of 100 mm and a magnification of 1000, the diagonal width of the field of view is 0.1 mm. For higher resolution, large magnification is important. However, such large magnifications are possible only if the NA of the system is high, typically exceeding 0.9 and ideally exceeding 0.95. The achievable NA here is a function of the aberration of the system. For an imaging system to achieve high throughput with low aberrations, it is desirable to have a field of view with a diagonal width greater than 100 micrometers and ideally the diagonal width may be greater than 1 mm. For illumination systems, such as projection optics for lithography, high NAs can be achieved without the limitations of fixed-size imaging sensors. Water immersion can be used to increase the NA above 1.9. For these systems, large fields of view are available with high numerical apertures, typically at magnifications lower than 10x (usually 1x or 4-5x reduction). A typical lithography system uses projection scanning and has a field of view of about 26 mm x 5 mm. Manufacturing wide-field, high-NA optics requires a system composed of many lens elements (e.g., 5-15), each of which must be polished and precisely assembled with high precision. Therefore, the overall yield of the optical system depends on the product of the yields of each of these precision lenses. This can lead to very low yields, making such lens systems prohibitively expensive or impractical.

One embodiment of the present invention reduces the requirement for multiple lenses in a lens system and emphasizes the fabrication of one or several precision corrector plates with complex profiles that can compensate for the reduced requirement for multiple lenses. avoid these problems Since only a few elements require high precision, the yield of the overall system can be improved to produce high NA, high field of view and high magnification lens systems.

12 shows an example of a multi-lens optical system according to an embodiment of the present invention.

In one embodiment, semiconductor optical imaging, lithography, metrology, microscopy, inspection, characterization, diagnostics, cameras and other systems requiring a multi-lens column as shown in FIG. 12. The nP3 process can be combined with RIE to fabricate elements for use in multilens optical systems for This process provides precise control over the profile of one or more optical elements that may be used in such systems. These elements may be nominally curved lenses (spherical, aspheric, freeform, toric, etc.) or nominally planar plates (eg windows). Also, in one embodiment, the use of a multi-lens optical system having one or more elements fabricated using the nP3 process may be combined with RIE. One or more of these nP3 elements can be part of the original system design (see FIG. 13), and the nP3 process will provide better optical performance with higher precision than current state-of-the-art and consequently a lower or similar cost structure. can Figure 13 shows an element 1301 fabricated using nP3, which is part of the original system, according to one embodiment of the present invention.

Design and fabrication of the nP3 element can be performed after measuring the aberrations and optical performance of the system without the nP3 element(s). One or more of these nP3 elements may also be custom correction plates (see FIG. 14) added to the original system to compensate for aberrations introduced in manufacturing and assembly of the system. 14 shows corrector plates 1401 fabricated using the nP3 process and added to the original system to improve optical performance and to mitigate design, manufacturing, and assembly tolerances for other elements of the system, according to one embodiment. do.

These aberrations may include on-axis, off-axis, chromatic, monochromatic, polarization and other aberrations. In one embodiment, these aberrations are measured after assembly of the system and prior to assembly of the nP3 correction plate(s). This allows non-nP3 elements of the optical system to be manufactured and assembled to relaxed tolerances, and one or more nP3 elements have the necessary manufacturing and assembly precision to compensate for errors in other elements. Here errors are measured prior to final assembly of the system. Thus, these nP3 elements are designed, manufactured and assembled after the other elements of the lens column have been assembled.

In one embodiment, these optical nP3 elements are used for darkfield imaging, lightfield imaging, confocal microscopy and high numerical aperture objectives.

In one embodiment, this optical nP3 element is used with an air gap during the assembly process.

Also, because of the nP3 process, these one or more nP3 elements could lead to new optical system designs, possibly with fewer elements or larger area elements, which use optical elements fabricated with conventional polishing or grinding processes. As in the designed optical system, desired optical performance can be obtained without requiring many elements. These one or more nP3 elements can also allow for a larger field of view and improve system throughput. Such one or more nP3 elements may also be made of materials such as SiO ₂ (including UV grade fused silica, fused quartz and various other glasses), Al ₂ O ₃ , MgF ₂ , CaF 2 , ZnS, and the like. Materials such as MgF ₂ and CaF ₂ (referred to herein as “unetchable materials”) react with commonly used etching gases (eg, oxygen, argon, CHF ₃ , HBr, Cl ₂ , etc.) to form volatile by-products. Because it may not form easily, it may be difficult or substantially non-etchable to etch in a plasma chamber. For these materials, intermediate sacrificial films of Si _x O _y , Si _x N _y , Si _x O _y N _z or other oxides and nitrides that can be etched using RIE are chemical vapor deposition (CVD) or physical It may be deposited on a substrate by a physical vapor deposition (PVD) process. This intermediate sacrificial layer can be profiled using nP3 in combination with RIE, so that the underlying unetchable material is substantially covered with the sacrificial material. This sacrificial material may have a refractive index that substantially matches the underlying non-etchable material to form a seamless interface with the optical element. Such sacrificial material may have a sufficiently thin thickness such that loss of optical performance due to the presence of the sacrificial material is minimized. This sacrificial material can be deposited on a textured layer of non-etchable material such that the interface behaves like a moth-eye structure and minimizes loss due to reflection. Such sacrificial material may also be polished or ground (eg, using a technique such as sub-aperture polishing) such that the material removal rates for both the sacrificial material and the non-etchable material are substantially similar. and the profile is substantially transferred to an unetchable material. Most polishing processes obey the Preston equation, which states that the rate of material removal is directly proportional to the polishing pressure and the relative velocity of the substrate. The proportional coefficient is called the Preston coefficient and is usually obtained experimentally. The polishing process can be designed or optimized so that the value of Preston's modulus is similar for both sacrificial and non-etchable materials. Any systematic error in the polishing or grinding process can be compensated for in the nP3 profiling of the sacrificial material.

Descriptions of various embodiments of the present invention have been provided for purposes of illustration, but are not intended to be exhaustive or limiting of the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used herein have been chosen to best describe the principles of the embodiments, practical applications or technical improvements to the technology found on the market, or to enable those skilled in the art to understand the embodiments disclosed herein.

Claims (29)

A method of manufacturing one or more elements in a multi-lens column, comprising:
dispensing ultraviolet (UV) curable droplets by inkjet onto a substrate;
forming a non-uniform liquid film by spreading and merging the inkjet droplets;
locally heating the film;
curing the film by exposing it to UV light, wherein the cured film together with the substrate forms an element of the multi-lens column; and
and performing optical metrology on the cured film and the substrate. According to claim 1,
A method of spreading and merging the inkjet droplets using a superstrate. According to claim 1,
The optical measurement is performed simultaneously with the formation of the non-uniform liquid film. According to claim 1,
wherein the element of the multilens column formed from the cured film and the substrate corrects optical aberrations of one or more other elements of the multilens column. According to claim 1,
The process of locally heating the film is performed using at least one of an infrared light source projected using a digital micromirror device array, distributed microheaters, and an infrared laser source mounted on a stage. how to be A method of manufacturing one or more elements in a multi-lens column, comprising:
Depositing a hardened film on the surface of an imprecise lens to correct external or intrinsic aberrations using a nanoscale precise programmable profiling process,
The nanoscale precise programmable profiling process,
dispensing ultraviolet (UV)-curable droplets by inkjet onto a substrate;
forming a non-uniform liquid film by spreading and merging the inkjet droplets;
locally heating the film; and
curing the film by exposing it to UV light; and
and transferring the profile of the cured film to the substrate by dry etching, wherein the substrate having the transferred profile of the cured film forms an element of the multi-lens column. According to claim 6,
A method of spreading and merging the inkjet droplets using a superstrate. According to claim 6,
The optical measurement is performed simultaneously with the formation of the non-uniform liquid film. According to claim 6,
wherein the element of the multilens column formed from the cured film and the substrate corrects optical aberrations of one or more other elements of the multilens column. According to claim 6,
The process of locally heating the film is performed using at least one of an infrared light source projected using a digital micromirror device array, distributed microheaters, and an infrared laser source mounted on a stage. how it is done. one or more optical elements fabricated using a nanoscale precision programmable profiling process and a dry etch process;
The nanoscale precise programmable profiling process,
dispensing ultraviolet (UV) curable droplets by inkjet onto a substrate;
forming a non-uniform liquid film by spreading and merging the inkjet droplets;
locally heating the film; and
curing the film by exposing it to UV light; and
and transferring a profile of the cured film to the substrate by the dry etching process, and the substrate having the transferred profile of the cured film is a multi-lens column forming an optical element of the multi-lens column. column). According to claim 11,
The one or more optical elements include corrector plates that correct for one or more of on-axis aberrations, off-axis aberrations, chromatic aberrations, and polarization aberrations. multi-lens column. According to claim 11,
The one or more optical elements are multi-lens columns used in one or more of semiconductor lithography, imaging, microscopy, inspection, characterization, metrology, and cameras. . According to claim 11,
The one or more optical elements may be used in one or more of darkfield imaging, lightfield imaging, confocal microscopy, and high numerical aperture objectives. lens column. According to claim 11,
The total aberration in the multi-lens column is better than λ / 10 peak-to-valley (PV) optical path difference error, and the λ corresponds to the wavelength of light. According to claim 11,
The total aberration in the multi-lens column is better than the λ/30 Root Mean Square (RMS) optical path difference error, and the λ corresponds to the wavelength of light. According to claim 11,
The multilens column of claim 1 , wherein the optical imaging quality of the one or more optical elements has a Strehl ratio greater than 0.95. According to claim 11,
The multi-lens column of claim 1, wherein the one or more optical elements have a numerical aperture greater than 0.90. According to claim 11,
wherein the one or more optical elements are made of one of SiO ₂ , UV grade fused silica, CaF ₂ , MgF ₂ , Al ₂ O ₃ and ZnS. According to claim 11,
The one or more optical elements are designed, manufactured, and assembled after the other elements of the multi-lens column are assembled. According to claim 20,
The one or more optical elements compensate for aberrations of the other assembled elements. According to claim 11,
The field of view of the multi-lens column has a diagonal width greater than 100 micrometers, and the multi-lens column is used for imaging. According to claim 11,
A field of view of the multi-lens column has a diagonal width greater than 1 millimeter, and the multi-lens column is used for imaging. According to claim 11,
The multi-lens column of claim 1 , wherein the field of view of the multi-lens column is greater than 250 square millimeters, and the multi-lens column is used for projection lithography. According to claim 11,
The one or more optical elements are made of an unetchable material in a reactive ion etching chamber, and a sacrificial material is deposited on the unetchable material. According to claim 25,
The multi-lens column of claim 1, wherein the non-etchable material has a textured interface with the sacrificial material. According to claim 25,
wherein the sacrificial material and the non-etchable material are polished at substantially similar rates. According to claim 25,
The sacrificial material is a multi-lens column comprising one of Si _x O _y , Si _x N _y and Si _x O _y N _z . According to claim 25,
The multi-lens column of claim 1 , wherein the sacrificial material has a refractive index substantially similar to that of the non-etchable material.

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